While there have been improvements in detection, treatment and prevention techniques, dental caries remains a prevalent condition affecting people of all age groups. If not properly and promptly treated, caries could lead to permanent tooth damage and even to loss of teeth.
In response to the need for improved caries detection methods, various dental imaging systems, such as intraoral cameras, have been developed for early caries detection. One problem that existing dental imaging systems have in common is a long delay period between the time that the tooth is initially screened and the image of the tooth is obtained and the time that a possible caries condition is identified or reported to the dentist. With existing systems, tooth screening (during which the images are obtained) and caries detection (during which the images are processed and analyzed to identify carious regions) are carried out as two separate steps. In practice, at an appropriate point during screening, a still image capture is first obtained from the tooth in response to an operator instruction. Then, in a subsequent step, the image data are processed and analyzed for carious conditions to provide the clinician with a processed image (possibly also accompanied by a report) indicating caries information, such as apparent location, size, and severity, for example. This caries information is available only after the conclusion of the tooth screening step and only after image processing/analysis steps are completed. When the caries information becomes available at this later time after screening, the dentist often needs to go hack and re-examine the imaged tooth in order to look more closely at the reported problem area. This delay is inconvenient and lengthens the duration of the examination session. It can be appreciated that there would be an advantage to a method and an apparatus that would provide more immediate feedback to the examining practitioner, so that problem areas can be identified and examined more closely at the time of screening. However, this advantage is not available with conventional systems, due to factors such as the difficulty of detection, the intensive computation requirements needed for many existing detection methods, and the large amount of image data that is required for each tooth.
To solve the long delay problem, commonly assigned U.S. Patent Application Publication No. 2009/0185712 (Wong et al.) describes using region growing and global threshold methods to determine or segment tooth areas and caries areas, respectively. While this approach is workable under some conditions, performance can be hampered due to illumination variation, compromising the accuracy and robustness of results.
Thus there remains a need for an apparatus and a method that are capable of providing more immediate feedback to an examining practitioner so that caries areas can be identified and examined more closely at the time of screening, yet with reduced sensitivity to illumination variation.